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Ghosts in the Trees

Last night, I was reminded of how unusual some of the insects we raise here in the Cockrell Butterfly Center are to most people. I had set up a table in the grand hallway of the museum to promote our outreach program, cleverly titled “Bugs on Wheels.” As soon as I left the Butterfly Center’s doors, I had drawn a crowd that didn’t seem to subside for the entire evening!

I think what grabs most people’s attention are our exotic walking sticks, which we have been displaying for several years. As soon as people see our giant prickly stick, they commence with “what on earth is that?” type of comments, and I love to educate them!

Walking sticks belong to the insect order Phasmatodea or Phasmida. This name comes from the Latin word phasma,which means ghost. It refers to their amazing camouflage skills, which in the right setting, can make them vanish right before your eyes! These insects are all herbivorous and harmless, having no venom or large mandibles for biting. This makes them an easy target for insectivores! So they have come up with some pretty fantastic ways to protect themselves from predators. These insects have simple metamorphosis, so the immature nymphs, look like tiny versions of the adult. Here at the butterfly center, we raise 5 different species of exotic walking sticks. I’d like to share a little about each one with y’all!

The Giant Prickly Stick, or Extatasomatiaratum, is one that really draws the crowds! The females are very large, 6 to 8 inches in length, and very fat! They range in color from light peach to dark red-orange. They are often – almost all the time, actually – mistaken for a scorpion. This is no accident, this species is native to Australia, the venom-capital of the world! They spend their entire lifetime hanging in eucalyptus trees feeding on the yummy foliage and easily folding themselves to resemble a dried up leaf.

If they are spotted by a potential predator, they will curl their abdomen to look remarkably like a scorpion. This warns predators that if they don’t want a nasty sting, they should stay far away. What a clever defense! Since they are, of course, completely harmless. They have a very soft exoskeleton which keeps them confined to the safety of the tree tops. If they need to do anything like lay an egg, they drop it to the leaf-covered ground. The females have small vestigial wings, but are incapable of flight. They can lay up to 1,000 eggs in their lifetime and can live a little over a year. The males are quite a bit smaller, very thin, and excellent fliers. They are equipped with much longer antennae than the female, which they use to sniff out a mate.

The Spiny Devil (Eurycanthacalcarata), is a close neighbor of the prickly stick; they are native to New Guinea. These adorable stick insects have very different habits. They are equipped with a very hard exoskeleton that is covered in hard spines, especially the legs! Since they are a harder egg to crack, they are not as attractive to eager insect-eaters, plus, they put up quite a fight! They can use their legs as a weapon by squeezing with all of their strength. I can speak from experience and say, it hurts!

When threatened, they can put on quite a show, raising their abdomen and back legs. We like to call it “the handstand of pain!” Since the female has the freedom of reaching the ground, she uses the pointy tip of her abdomen (her ovipositor) to lay her eggs deep in the soil. The male and female look quite similar, both are wingless and they are nearly equal in size. Both sexes can live for about a year and a half as adults – not bad! The male does have one distinguishing characteristic, a single very large spine on his hind femur.

They are very territorial and use this spine for fighting. They can seriously injure or even kill another male during combat. Still want to mess with these guys? Well, the males can also emit a very foul chemical that smells just like a skunk. However, they are usually pretty laid back.

The Phylliumcelebicum or moving leaf insect is a breath of fresh air. These leaf mimics are petite, dainty, have no spines or smells, and are 100 percent cute! They inhabit the rain forests of Malaysia.

Since they have no other defense mechanisms, their camouflage has to be absolutely perfect, and well, see for yourself! They also spend their entire lives in the canopy, dropping their eggs to the ground haphazardly. The female, pictured right, has larger wings than the Giant Prickly Stick, but their only function is camouflage. The male is half the size of the female and he’s an amazing flyer! These live a little under a year and we love to have them around.

I actually noticed something very interesting from observing them. The outer 1/2 inch of the female’s body is only a layer of skin, and all of the organs are arranged down the very middle of the abdomen. This is important because I started seeing a couple of them missing chunks of their abdomen, but they didn’t appear to be injured. I’m sure they get nibbled on by several herbivores in the wild – it’s a pretty cool adaptation.

Sharing the same rain forest is the Giant Jungle Nymph (Heteropteryxdilatata). They are spectacular, very large and beautiful. The females are bright green and usually 7 inches in length with a wide abdomen. They have small wings which they rub against their bodies to produce a hissing noise. Their thorax, abdomen, and legs have rows of sharp spines. When disturbed they thrash around violently and they also do “the handstand of pain.”

They spend most of their time in the trees and only travel to the ground to lay their eggs. The male is brown and only about 4 inches long. They have bright crimson hind wings and are very showy. They are always very nervous and thrash around a lot! This species is harder than the others to raise. They need high humidity and they take a long time to develop.

The eggs take around 17 months to hatch and the nymphs take over a year to develop into adults. This species can be very aggressive, but we always end up with a few that can be handled, they are very curious and active.

The last resident of southeast Asia is the Annam stick insect (Baculumextradentatum). These look very similar to our native walking sticks. They are very slender and really resemble a twig. These are interesting little creatures. When disturbed, they will essentially go limp and flop to the ground. It’s really the only option for them since they are so defenseless.

The most interesting thing about this species is that they can be completely parthenogenic. This means that the females can reproduce without males. We do have males in our populations and it is a full time job making sure we don’t have too many individuals. They are egg-laying machines. Their life span is about a year and males and females look very similar, but the males are much smaller.

These walking sticks are some of the most amazing insects I’ve worked with. I’m so impressed with their diversity and beauty. Next time you see them in the Entomology Hall or in the Grand Hall, come by and see them, you’ll certainly be amazed!

About Erin M

As an entomologist at the Cockrell Butterfly Center, Erin designs, creates, and maintains exhibits for the Entomology Hall, raises and cares for live insects and insect relatives, and educates the public about the wonderful world of bugs.